WARNING! A new way for MMMs to fail including your precious V3!
 

Today when i was out bashing i went over a small jump and as i landed my Losi 8T Tekno conversion just died. I went over to it and sure enough it was my 5th MMM that had failed. I couldnt figure out what went wrong cuz i had just barely updated it with the most recent firmware.
After closer inspection i noticed that when i hit the bump my battery must have jolted forward just enough to bump the connectors on the ESC and push them into the heatsink. The result was two connectors touching the heatsink at the same time and....ZAP! Shorted out and fried my ESC. this is a major design flaw IMO with the MMM. Granted only the Losi 8 Tekno conversions are probably capable of this due to where the battery is mounted but when i looked at the MMM the connectors sit approx 1mm away from the heatsink. it doesnt take much force to move those connectors 1mm.
So i came up with a simple fix. i wrapped electrical tape around the connectors to keep there from being any connectivity should they touch the heatsink. anyway, just a heads up for all you losi 8 tekno owners with MMMs. i would make the change now and MMM owners in general it is something to consider.

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Damn, unlucky. Is everything else ok? (motor, battery etc.)

If they come stock with a fan, you'd think they could get away with a slightly smaller heatsink. At least one that doesn't come so close to the power connectors with a small plastic piece buffering that area between the two. Either that or do away with the connectors and have pre-soldered wires coming out.

i have now loaded in my first of 4 v3 MMMs i have, or rather the first that i have recieved out of 4 that Castle owes me. everything seems good. Neu motor seems good and batt is ok too. thankfully. i was looking at it again trying to ascertain exactly what happened and the best that i can come up with is just what i mentioned before. i can see the other connector that sits against the heatsink so all that had to happen was for one more connector (the wrong one) to touch up against it.
so i inspected my v3 before installing and that is the one i put the tape around. as you can see i did not put tape around the positve battery connnector like i did all the other connectors. the reason i didnt put tape around that one is because it rests against the heatsink and i couldnt get tape around it. however, as long as all the others are covered it wont matter. anyway, this is definitely an issue that Castle should look into.

The other possibility is that the male connector slipped out of the female connector and as it did managed to end up resting on top of the female and against the heatsink causing the short. in this scenario anyone could fall victim, not just Tekno losi 8 owners. either way, none of this would have happened if the heatsink were smaller and/or if one connector didnt already touch the heatsink and/or if the heatsink were generally better protected from the connectors.

Just buy some 8mm heat shrink and use them instead of tape. It will work better.

I'd be surprised if Castle covers this w/o a fee.. you obviously took the plastic cover off changing castles design and voiding the warranty. With the heat shrink that castle has on the motor output wires and the support the plastic case gives near the top it keeps this part from moving at all, I say the only design flaw is in your own changes from the looks of it. I guess we will see, but I've been running MMM's since the first batch of V1's and never had this issue, still have a v2 going strong in my erevo and 2 v3's in my 8ights (truck and buggy).

PS you may want to try a new mounting location in your 8t

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I'd prefer it to have a big heatsink assisted by a fan, the cooler the better. I've got an old passively-cooled CPU sitting here with a similar heatsink on it :lol: Stock they're pretty tough, but when you ram a battery into them (was the case even on it when it was damaged?) things tend to bend. I'd prefer wires soldered to the board like all their other ESCs, but they insist this design is better :whistle:

Here's my situation now. What if one doesn't have the 1mm space between the plugs and the heatsink, what do you do then?

Take a pic and E-Mail it to Castle. They'll have you send the ESC back and they'll send you a fixed ESC or a replacement within a month or two.

The MMMs remind me of the first gen VXL systems that used the same design. It wasn't long before they updated it to wire leads with bullets. Castle should have learned from someone elses mistake.

My thoughts exactly. Patrick's response was that with the MMM's connectors being so much larger there was more solder holding it to the board so there wouldn't be a problem...I think if I end up buying one and it has bullets on the board I'll remove them in favor of wires.

why dont they just replace those damn plugs with wires... it would have save many MMM's.
what do we benefit with those plugs, compared to wires?

I'm not entirely sure...most motors you buy come with 1-2 inches of wire coming out the back so you have to make an extension to go from the ESC to the motor, makes no sense to me either. The CC Neu motors are supposed to have long motor wires so they'll plug right into the ESC but IMO it's a bad idea still.

They couldn't have missed them :lol::

http://www.rc-monster.com/forum/showthread.php?t=15249

I remember reading that post, that was pretty stupid that it came like that. IDK how it passed QC unless they don't check their ESCs before shipping them.

When I first saw the bullets on the newer MMM's I thought it was cool, until I installed it.

I would much rather have wire directly soldered to the board.

The bullets are just one more connector we don't need.

Not to mention the clearance issue. In a Revo or truggy I guess it's not such a big deal. But in a buggy with a tight body it is a big deal.

Gimmie my old style wires back. :mdr:

I took the bullets off of my v3 and direct soldered the wires to the female side of the bullet at 90 degrees. So far so good. :tongue:

I do remember that Patrick mentioned testing the MMM and that touching the heatsink to the bullet connectors did not do anything. He said that they could not cause a failure when they tested this issue...

I bent the fins away from the connectors on my MMMs but I may also put some shrink around them too. Time to take them all apart again!!! Whoo hoo.

I'm still thinking if I should take the plugs out. If I do, I'm going to direct solder wires on there, but not facing up. I'll have the wires laying down and make a hole so they'll exit from the back. I would reather have them like that as most application will work better that way. It should be an option that the customer can select how they want there wires to be and if they want plugs and all.

Just a warning guys...you'll need a super powerful iron to desolder those bullets, and with the amount of copper in the PCB, you risk melting solder on other components on the board (as I once learnt with my MM). If this is really causing an issue, I'd just bend the relevant heatsink prongs out of harm's way, and maybe just shrinkwrap the plugs IMO?

I must admit, I can't see how a that socket would've been able to flex the PCB so much as for it to touch the PCB as it's so light (it would take a relatively high impact on the plug for that to happen...or at least, that's how it seems to me), so from where I am it sounds more likely that the plug slipped out and shorted. But even then, Patrick's said this shouldn't be able to happen, so I dunno. Strange...

I did bend some fins back, but when you look at the pics I took the part hat is touching the plugs is the bottom of the heat sink. I haven't ran my MMM yet and if Patrick need to look at the problem it has, I'll be more than glad to send my Monster for him to inspect it.

this problem has nothing to do with modification. i have a v2 still going strong too. i love them despite the ones that have failed. my motor lead wires are have heatshrink on them but that doesnt matter if either the female connector is up against the heatsink or if the male portion of the connector decides to come out and rattle against the heatsink/female connector at the same time. there isnt heatshrink on the part that inserts into the connector, remember! and go look more closely at your unmodified MMMs. there is nothing between the connectors and the heatsink. there is a little plastic between the connctors themselves but nothing stopping them from hitting the heatsink in a hard hit. think these things through, stum.

really, they tested this? hmmm. well, remember guys, this is probably a rare occurence but i thought everyone should know. i am not sure if this calls for de-soldering and everything but i dont know. maybe thats the best route. it seems we have been having to mod the MMMs since day one to make a better mousetrap, huh.

Ya he said that but I bent the fins on the heat sink & put shrink tube over the bullets anyway to avoid this.

Is there enough space to slide a piece of lexan (or any other non-conductive material) in between the connectors and heatsink? If there was constant rubbing, anything would get worn away, but sounds like it just needs a little barrier sometimes...

i still like the way the v1 was with wires. The bullets just seem to add a huge pita.

I agree. I was thinking about removing the HS on my MMM, resoldering the wires so they are on the other side of the PCB, and attaching the FETs to an aluminum tray/mounting plate/heatsink. Similar to how the Quark is designed...

Honestly, to me, it doesn't look like the problem was the bullet shorting to the heatsink. To me it looks more like there was excess resistance in that connector that caused the it to melt. I had some excess resistance in one of my bullets but I caught it in time because it was on the battery side and the symptoms were obvious. Being on the motor side I'm not sure how noticable the symptoms would have been. It looks like the biggest part of your bullet that is burned off isn't even on the side of bullet closest to the heasink.

I agree.

What no fan? Anyways I too think the bullets are unnecessary. I would love wires with plugs on the end.

http://www.rc-monster.com/forum/show...599#post224599

I like the onboard bullets. Cleans things up a bit, and there are only 3 solder joints on each route going to the motor instead of 4 with plugs on the wire.

Looking at it again I also agree w/ your assessment. I bet if that one was a sliding out it and only had a partial connection it would have done this as well.. give it a try it's pretty hairy.



PS RYU (from comment above), you are dead wrong.. take a look again, if you leave the MMM in the stock form and use the provided castle motor leads the heatshrink on the motor leads are resting firmly against the top plastic just over the exposed finned area, making it IMPOSSIBLE for the connector to hit unless the shrink wore off those wire leads. I have looked it over several times.. and thought it plenty through.

You know the heat sink is not part of the elec circut in the esc. So if it did touch the connector nothing should happen. Also since it is alum it would have more blown out of it than the bullet if it was part of a short. I think the bullet connector was the problem here.

ive noticed spots on my battery connectors, where it seems like its been arcing to the female plug.... i really want a v1 which works!! lol. hope they fix this soon!

I've noticed most male bullet connectors with casting flash on the edges. I always file the flashing off so you only get the flat part of the connectors touching.

True, the HS is not part of the circuit, but it can act like a bridge if two bullet connectors touch it at the same time. But yeah, you'd think the HS would show more arc pitting than the bullet if that was the case.

....making it impossible for the MALE connector to touch but not impossible for the FEMALE connector to touch. the female connector is what i am referring to. or also the male portion that inserts in the female. (now i am sounding like sex ed.:lol:) unless you heatshrink it, tape it, bend heatsink, it can/or already is touching. but that is besides the point now. you mentioned something that may be the answer. that if the male connector came out and was touching the female connector lightly that it could cause this short. is that correct? if so that is what i am thinking happened at this point. curious though? how does this cause a short just by lightly touching if it is still touching the right connector? also, should i change this connector? will it affect the performance? if the connector has the gold finish rubbed off does this also affect performance? here are some more pics to help us find the answer and help us see eye to eye.

my camera is not the best but you can see the heatshrink is fine. aside from that though look at the connector. it has a round shape zap in it like where it rested on top of the female plug on the esc. so i was thinking that it must have slipped out, bounced around, and touched the heatsink and female connector at the same time whilst one of the batt. famales on the esc is up against the heatsink also, causing the short. but if the light connection itself could have caused this that is likely the answer. any input on this? the last pic is of me holding a female end to the male end that shorted to show how the tip of the male connector has the indentation of the female connector on it. (whew! long winded explanation)

ps. sorry but for some reason i could only post links to the pics.

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So, yeah, this whole not enough space for the heatshrink on your connectors thing kinda bugs me.
I don't like the amount of pressure there is between the heatsink and the shrink tubing on my motor wire bullets. There will be metal on metal contact there after only a few runs...at the very least, it is something to worry about.
So, what do I do? Just wait'l something goes wrong or send it back to them asking for one that leaves anough of a gap that I don't have to worry about these connectors shorting to the heatsink?

What the hell, Castle? Nowhere during your quality checking did anyone notice this might present an issue? I mean, why would anyone wanna put shrinkwrap on their connectors? Of course people will want all 3 motor leads making contact with the same aluminum heatsink...:whistle:

Think I'll see what I can manage with a scap of lexan, but I'm really getting sick of the whole Castle mantra of "fix it yourself before using".

If I wanted it to be like this, I'd be buying caps, fets and circuitboards and making my own.

It looks to me like the male bullet was not pushed in all the way and it just overloaded the connection.

Hmmmm --- Again, we checked, and checked and checked this issue--- OVER AND OVER AND OVER AGAIN. We shorted the bullets, scraped off the anozide and pushed the heatsink intot he bullets, etc. Never could we even get ONE failure to occur.

So don't berate us, we tested the hell out of this supposed "problem" and found there to not be a problem.



Besides -- I don't think the issue was a pair of bullets pushed into the heat sink -- or there would have been two bullets that showed damage. And the heat sink itself would have also have burn damage which isn't evident in the pictures. It could very well have just been a loose connector that caused that type of damage (as the male connector made poor contact, it burned the edges of the female.)